Dielectric resonator oscillator and voice control device

ABSTRACT

The invention relates to a dielectric resonator oscillator, comprising a dielectric resonator contained in a resonant cavity in order to generate a signal oscillating at a predetermined central frequency, the dimensions of the resonator and the limiting conditions in the cavity being capable of determining the resonant frequency of the resonator. It comprises means sensitive to acoustic pressure waves capable of modifying the distribution of the electromagnetic fields in the cavity as a function of said acoustic pressure waves. The invention also relates to a voice control device equipped with an oscillator according to the invention. Particular application to remote voice control devices for controlling domestic equipment.

This application claims the benefit, under 35 U.S.C. §365 ofInternational Application PCT/FR00/03615, filed Dec. 20, 2000, which waspublished in accordance with PCT Article 21(2) on Jul. 12, 2001 inFrench and which claims the benefit of French patent application No.9916866 filed Dec. 31, 1999.

The invention relates to the field of signal transmissions, especiallywithin the super-high frequency (SHF) range. More particularly, theinvention relates to a dielectric resonator oscillator for transposingaudio signals into the SHF frequency range. The invention also relatesto a voice control device.

SHF dielectric resonator oscillators (DROs) are commonly used in devicesfor transmitting SHF signals, enabling high-performance oscillators ofsmall size and of low cost to be obtained. They are especially used as alocal oscillator for frequency transposition in low-noise converters forsatellite reception.

FIG. 1 shows schematically a dielectric resonator oscillator 1 with atuning screw, of the prior art. The latter comprises an electromagneticcavity 2 delimiting by its walls 3 a dielectric resonator 4 coupled to afirst microstrip line 5. A circuit 7, illustrated in FIG. 2 showinganother resonator of the prior art, the rest of which will be describedbelow, is common to the two resonators and fulfills the same functions.Consequently, the description of the main components of this circuit 7will be made with reference to FIG. 2. In general, in order to simplifythe description, the same references will be used to denote the elementsfulfilling identical functions in the present application. The couplingline 5 is, on the one hand, connected to the active circuit 7 and, onthe other hand, to an impedance matching load 6. The active circuit 7comprises an active element 8, of the bipolar transistor or FET type, anelement 9 destabilizing the active part, for example of the LC circuittype, and an output impedance matching element 10, of the microstripline type. It is known that the RLC circuit equivalent to the resonatoris the source of damped oscillations, the damping of these oscillationsbeing due to the resistive part of the RLC circuit. This active circuitwith a negative resistance then has the function of providing the energyneeded to maintain the oscillations, so that the signal delivered to anoutput 12 of the oscillator is an undamped oscillating signal. It isalso known to a person skilled in the art that the assembly formed bythe resonator coupled by the microstrip line to the active circuit mustexhibit oscillation conditions favorable to the oscillation frequencysought. In the oscillator of FIG. 1, a screw 13 enters the wall 3 of thecavity opposite the dielectric resonator 4. Its degree of penetration ina direction perpendicular to the surface opposite the resonatorgenerates a disturbance in the distribution of the electromagneticfields in the cavity and, subsequently, a modification of the resonantfrequency of the equivalent resonant circuit. Thus, varying the distanced between the end part of the screw entering the cavity and the uppersurface of the resonator involves modifying of the frequency of thesignal generated by the oscillator. However, this type of oscillator,involving manual adjustment of the distance d, does not allow the finevariations around a central frequency to be faithfully complied with,and without distortion; it is therefore not suitable for transmittingaudio signals.

In order to overcome problems linked to the mechanical adjustments asmentioned above, oscillators called electronic oscillators are alsoknown, as illustrated in FIG. 2 showing a dielectric resonatoroscillator with a varactor. A varactor 11, connected to a secondmicrostrip line 17 coupled to the dielectric resonator, receives acontrol signal S_(c) of variable voltage indicating an audio signal tobe transmitted. The resonator-varactor assembly behaves like a resonantcircuit setting the oscillation frequency of the oscillator. Thus, thevariation in the voltage delivered by the signal S_(c) modifies theoscillation frequency of the oscillating circuit 7. However, the use ofa varactor has the effect of degrading the phase noise of the oscillatorand consequently of degrading the quality of the signal generated at theoutput of the oscillator.

The object of the invention is to overcome the problems of the prior artby providing a dielectric resonator oscillator for transposing audiosignals.

To this end, the invention is a dielectric resonator oscillator,comprising a dielectric resonator contained in a resonant cavity inorder to generate a signal oscillating at a predetermined centralfrequency, the dimensions of the resonator and the limiting conditionsin the cavity being capable of determining the resonant frequency of theresonator. A means sensitive to acoustic pressure waves is capable ofmodifying the distribution of the electromagnetic fields in the cavityas a function of said acoustic pressure waves. The means sensitive toacoustic waves comprise a membrane which is movable under the effect ofacoustic waves, said membrane engaging a metal coil in the cavity.

Thus, the means sensitive to acoustic pressure waves directly change intime with the acoustic pressure exerted at one of the inputs of saidsensitive means. In this way, the invention makes it possible togenerate a signal modulated directly by the audio signal at this input.

According to one embodiment, said means sensitive to acoustic pressurewaves comprise acoustic transducer means for converting the acousticpressure waves into a displacement of at least part of detachable meansfacing the resonator, the displacement of at least part of thesedetachable means under the effect of acoustic pressure waves beingcapable of modifying the distribution of the electromagnetic fields inthe cavity.

According to one embodiment, the displacement of said detachable meansis carried out in the form of vibrations.

According to one embodiment, the means sensitive to acoustic wavescomprise a membrane which is movable under the effect of acoustic wavesand can engage a metal coil in the cavity.

According to one embodiment, the oscillator comprises adjustment meansto adjust the central frequency of the resonator.

According to one embodiment, said adjustment means comprise anadjustment screw which can be engaged in the cavity in order to modifythe distribution of the electromagnetic fields therein.

According to one embodiment, the oscillator comprises switching means toswitch the modulation by acoustic waves of the signal generated by theresonator to modulation by data transmitted over a channel.

According to one embodiment, an active dipole is coupled to saidresonator by coupling means in order to maintain the oscillations.

The subject of the invention is also a voice control device,characterized in that it comprises an oscillator according to theinvention.

Other characteristics and advantages of the present invention willbecome apparent from the following description of exemplary embodiments,taken by way of nonlimiting examples, with reference to the appendedfigures in which:

FIGS. 1 and 2, already described, show two dielectric resonatoroscillators of the prior art,

FIG. 3 shows a dielectric resonator oscillator according to oneembodiment of the invention,

FIG. 4 illustrates a curve showing the variation in frequency, to whichthe signal output from the oscillator of FIG. 3 is subject, as afunction of the distance d,

FIG. 5 shows a remote control device according to the invention.

FIG. 3 illustrates an oscillator 14 according to the invention. Itcomprises a resonant cavity 2 inside which there is a resonator 4electromagnetically coupled to a microstrip line 5. The line 5 connectsa load 15 to an active circuit 7. The active circuit comprises, at itsinput connected to the line 5, a transistor of the FET type, whosesource is connected to a circuit, for example of the LC type connectedto ground, whose role is to make the transistor stage unstable, andwhose drain is connected is to a network 10 for matching the outputimpedance of the oscillator.

The cavity comprises an opening 16 in which the body of a microphone 17is engaged. The upper part 171 of the microphone 17 is oriented towardfree space and can receive acoustic pressure waves, in particular ordersin voice form from a user while the lower part 172 of the microphone isitself facing the upper part of the resonator. The base of the upperpart 171 receiving the voice of the user narrows down to a membrane 18in contact with a metal coil 19. The latter is capable of moving in thedirection perpendicular to the resonator under the effect of thevibration of the membrane receiving acoustic waves.

Thus, the mechanical vibration of the membrane with its coil enables theacoustic pressure exerted by the user to be measured, translating hisvoice. The mechanical modulation of this membrane with its coil modifiesthe properties of the cavity, the consequence of which is the modulationof the instantaneous frequency of the SHF signal created by theresonator (for example at 5.8 GHz) in synchronism with the voice signalto be transmitted. One advantage of the invention arises from thesimplicity of the microphone used in the present embodiment, which islacking its magnet.

For further information, reference may be made to chapter II relating tothe use of dielectric resonators, page 30 et seq. of the work,“Composants, dispositifs et circuits actifs en micro-ondes” [Microwaveactive circuits, devices and components] by P. F. Combes, J. Graffeuiland J. F. Sautereau, Dunod University Publishing, and the article“Current techniques for tuning dielectric resonators” by B. S. Virdee,in the journal “Microwave Journal”, October 1998.

As shown in FIG. 4, since the resonator is centered on a centralfrequency F₀, a modification of the distance d equivalent to δd1 leadsto a change in frequency δF₀ of about 5%, which is unimportant to theoscillator performance. This small variation δF₀ can be considered aslinear or almost linear depending on the displacement δd1 of the coil inthe cavity, which provides a direct modulation by the audio signal ofthe signal generated by the resonator, without distortion thereof.

According to an additional characteristic of the invention, a mechanicaltuning screw 180, which can be adjusted from outside the cavity 2 andwhose part 181 engaged in the cavity is laterally opposite the resonatorand is positioned so as to be able to adjust the central frequency ofthe oscillator as necessary, is shown in FIG. 3 in dotted lines. Alsoillustrated in FIG. 3 in dotted lines, according to an additionalfeature, is a connection 20 connecting, via a resistor 21, themicrostrip line 5 to a microprocessor 22 generating a significantdigital signal for the selection by the user of a command 24 from acommand table 23. According to the latter embodiment, the signalgenerated by the resonator is either modulated by the displacement ofthe coil 19 generated by the acoustic waves received at the membrane, orby the data transmitted by the microprocessor in the form of pulses.This option of choosing the modulating signal is enabled by the use of aswitch (not shown in FIG. 3), which allows transmission of the voice orof the data. One application of this mode is shown in FIG. 5,illustrating a remote control device for controlling any controllableappliance, especially a domestic appliance (television set, videorecorder, camcorder, disk or digital cassette reader/recorder, etc.).

The remote control device 25 illustrated in FIG. 5 comprises, in aconventional manner, a keyboard 26 having buttons 24 including a standbybutton 27 and a volume increase and decrease button 28, a digital pad 29in particular allowing a channel to be chosen, and a high-frequency (HF)signal emitter 30. The remote control device further comprises amicrophone 17 and a switch 31 for selecting the communication mode thatthe user wishes to establish, namely a voice mode corresponding to a“voice” button in which the signal generated by the resonator ismodulated by the voice of the user, and a touchpad selection modecorresponding to the “touchpad” button in which the signal generated bythe resonator is modulated by the signal generated by the microprocessorwhich depends on the buttons actuated.

Of course, the invention is not limited to the embodiments described inthe present application. There are various sorts of voice commands. In anonlimiting manner, mention will first of all be made of tuning into achannel. In this case, the user pronounces the name allocated to thechannel or the corresponding number.

The voice command may also be used to simplify operations which requiresuccessive actions when they are controlled by touchpad. For example, inorder to control the brightness using the remote control keyboard, it isnecessary first to access a menu displayed on the screen of the receiverand next, to select from this menu, by means of one or more operations,the brightness command. With the voice command, it is not necessary tocarry out successive operations. It is enough to pronounce, for example,the word “brightness”. In this case, the brightness can be increased ordecreased either by a voice command, or using the conventional increaseand decrease buttons (“plus” and “minus”) on the remote control box.

Of course, the application is not limited to the voice-activated remotecontrols but can be envisioned for voice commands of another type (wirefor example) or else a microphone.

What is claimed is:
 1. A dielectric resonator oscillator, comprising: adielectric resonator contained in a resonant cavity in order to generatea signal oscillating at a predetermined central frequency, thedimensions of the resonator and the limiting conditions in the cavitybeing capable of determining the resonant frequency of the resonatormeans sensitive to acoustic pressure waves capable of modifying thedistribution of the electromagnetic fields in the cavity as a functionof said acoustic pressure waves wherein said means sensitive to acousticwaves comprise a membrane which is movable under the effect of acousticwaves and can engage a metal coil in the cavity.
 2. The oscillator asclaimed in claim 1, wherein said means sensitive to acoustic pressurewaves comprise acoustic transducer means to convert the acousticpressure waves into a displacement of at least part of detachable meansfacing the resonator, the displacement of at least part of thesedetachable means under the effect of acoustic pressure waves beingcapable of modifying the distribution of the electromagnetic fields inthe cavity.
 3. The oscillator as claimed in claim 2, wherein thedisplacement of said detachable means is carried out in the form ofvibrations.
 4. The oscillator as claimed in claim 1, wherein saidoscillator comprises adjustment means to adjust the central frequency ofthe resonator.
 5. The oscillator as claimed in claim 4, wherein saidadjustment means comprise an adjustment screw which can be engaged inthe cavity in order to modify the distribution of the electromagneticfields therein.
 6. The oscillator as claimed in claim 1, wherein saidoscillator comprises switching means to switch the modulation byacoustic waves of the signal generated by the resonator to modulation bydata transmitted over a channel.
 7. The oscillator as claimed in claim1, wherein an active dipole is coupled to said resonator by couplingmeans in order to maintain the oscillations.
 8. A voice control device,including an oscillator, said oscillator comprising: a dielectricresonator contained in a resonant cavity in order to generate a signaloscillating at a predetermined central frequency, the dimensions of theresonator and the limiting conditions in the cavity being capable ofdetermining the resonant frequency of the resonator, a means sensitiveto acoustic pressure waves capable of modifying the distribution of theelectromagnetic fields in the cavity as a function of said acousticpressure waves wherein said means sensitive to acoustic waves comprise amembrane which is movable under the effect of acoustic waves and canengage a metal coil in the cavity.
 9. The oscillator as claimed in claim8, wherein said means sensitive to acoustic pressure waves compriseacoustic transducer means to convert the acoustic pressure waves into adisplacement of at least part of detachable means facing the resonator,the displacement of at least part of these detachable means under theeffect of acoustic pressure waves being capable of modifying thedistribution of the electromagnetic fields in the cavity.
 10. Theoscillator as claimed in claim 9, wherein the displacement of saiddetachable means is carried out in the form of vibrations.
 11. Theoscillator as claimed in claim 8, wherein said oscillator comprisesadjustment means to adjust the central frequency of the resonator. 12.The oscillator as claimed in claim 11, wherein said adjustment meanscomprise an adjustment screw which can be engaged in the cavity in orderto modify the distribution of the electromagnetic fields therein. 13.The oscillator as claimed in claim 8, wherein said oscillator comprisesswitching means to switch the modulation by acoustic waves of the signalgenerated by the resonator to modulation by data transmitted over achannel.
 14. The oscillator as claimed in claim 8, wherein an activedipole is coupled to said resonator by coupling means in order tomaintain the oscillations.